Development of Hard-Tissue Substitute by Superplastic Deformation of Carbonate Apatite

近年来，磷酸钙已被用作生物材料。我们以前报道过，烧结碳酸磷灰石具有比羟基磷灰石和β-TCP更高的生物相容性，可以广泛应用于骨填充和替代材料等生物材料。碳磷灰石陶瓷在高温下也表现出明显的塑性变形。为了利用这种高塑性变形能力将碳酸磷灰石用作任意形状的硬组织替代材料，本研究对塑性变形（超塑性变形）的发展条件和变形量进行了基本评价。将烧结的碳酸盐磷灰石置于连接到Survopulser（Shimazu Co.）的电炉中。通过氧化铝夹具以0.2Kn施加压力，直到样品被加热到指定温度。此后，将压力增加到10 Mpa作为初始载荷。测量了碳磷灰石试样的线性尺寸， 关于我们 保温2小时，观察其塑性变形行为。在变形之后，对样品进行SEM和X射线衍射分析，并评估其物理性质的变化。结果表明，当初始载荷为10 MPa时，在700℃时发生轻微的塑性变形。塑性变形量随保温温度的升高而线性增加，在800℃时达到80%左右。当用SEM观察时，变形后的试样似乎由较大的晶粒组成。加载前试样中存在较大的孔隙率，加载后孔隙率降低。X-射线衍射分析表明，在变形后结晶度的改善和轻微程度的晶体取向。这些结果表明，变形后的物理性能得到改善。因此，烧结的碳酸磷灰石在较低的温度下具有超塑性。因此，如果对超塑性变形能力进行适当的载荷、温度和时间评估，各种形状的烧结碳酸磷灰石可用作硬组织替代材料。

In recent years, calcium phosphates have been used as biomaterials. We previously reported that sintered carbonate apatite has higher biocompatibility than hydroxyapatite and β-TCP, and can be widely applicable as biomaterials such as bone filling and replacement materials. Carbonate apatite ceramics also shows marked plastic deformation at high temperatures. To use carbonate apatite as hard tissue substitution materials with arbitary shapes utilizing this high plastic deformability, basic evaluation of the conditions for the development of plastic deformation (superplastic deformation) and the amount of deformation was performed in this study. Sintered carbonate apatites were placed in an electric furnace attached to a Survopulser (Shimazu Co.). Pressure was applied via an alumina fixture at 0.2 Kn until the specimen was heated to a designated temperature. Thereafter the preasure was increased to 10 Mpa as an initial load. The linear dimension of the carbonate apatite specimen was mea … More sured for 2hr, and the behavior of plastic deformation was examined. After the deformation, SEM and X-ray diffraction analysis of samples were performed, and changes in their physical properties were evaluated. As a result, when the initial load was 10 Mpa, slight plastic deformation occurred at 700℃. The amount of plastic deformation linearly increased with an increased in holding temperature, reaching about 80% at 800℃. When viewed with SEM, the specimens appeared to be composed of larger grains after the deformation. Considerable porosity were present in specimen before the load application, but the porosity decreased after the load application. X-ray diffraction analysis revealed the improvement in crystallinity after the deformation and a slight degree of crystal orientations. These results suggested improvement in physical properties after the deformation. Thus, sintered carbonate apatite has superplasticity at a comparatively low temperature. Thesefore, if appropriate load, temperature, and time are evaluated for the superplastic deformability, sintered carbonate apatite with various shape can be used as hard tissue substitution materials Less